User input for an if/else statement

When you compare two Strings in Java with the == operator, they are compared to see if they are the same object, rather than whether they contain the same text. So, you could type "yes", and when you use if (answer == "yes") the comparison fails, because the object you got back from UI.askString is a different object, stored at a different place in memory, than the String the compiler generated from the literal "yes".

To compare the value of the two Strings you need to write answer.equals("yes"), or "yes".equals(answer). Either one will work, and will call the equals method of the String class, which will compare the actual text.

The latter syntax, "yes".equals(answer), is often recommended because it will not cause a NullPointerException, even if the variable answer is set to null. This is because the equals method handles null and simply returns false. If, on the other hand, you used the answer.equals("yes") form, and answer was null, you would be trying to invoke a method on null and an exception would be thrown.

what you are looking for is a dialog box. Here is oracle examples, with code. It is more than I can write here. There are ton of yes, no boxes and detection's of user input with them.

http://docs.oracle.com/javase/tutorial/uiswing/components/dialog.html

Quick answer:

int dialogResult = JOptionPane.showConfirmDialog (null, "Would You Like to Save your Previous Note First?","Warning",dialogButton);
if(dialogResult == JOptionPane.YES_OPTION){ ... }

Other choices ...

 YES_OPTION, NO_OPTION, CANCEL_OPTION, OK_OPTION, and CLOSED_OPTION

For a command line program you need...

import java.util.Scanner;

The code will look like ...

Scanner in = new Scanner(System.in);
String line = in.nextLine();

//ask them to write yes, no, whatever

if(line.equal("yes"){ }
else if (line.eqals("no") {}
else {}

using MikeG010590's answer, you can try:

Scanner in = new Scanner(System.in);
    String line;
    System.out.println("you want to continue?");
    Boolean exit = null;
    do {
        line = in.nextLine();
        switch (line) {
            case "yes":
                exit = false;
                break;
            case "no":
                exit = true;
                break;
            default:
                System.out.println("Please enter yes or no");
                break;
        }
    }
    while (exit == null);
    System.out.println(exit ? "Thank you. Goodbye" : "Lets go");